It's possible, yes.
One way would require a 2nd wireless card for the laptop, then 'share' the internet connection via the 2nd wireless card.
The way to do it without spending any money would require two pieces of software on the laptop.
You'd need this:
Microsoft Virtual WiFi - http://research.microsoft.com/netres/projects/virtualwifi/ - this things is cool - it clones your wifi card...hehe
Then also this thing:
2HotSpot - http://www.2hotspot.com/ - this one lets you create your own virtual wifi hotspot.

...so now by doing this, any other wireless computer you have within range of the laptop could use the connection......pretty neat, huh?

>Just for the sake of argument...
>
>There is a desktop transmitting a wireless connection. Then a laptop with a Cisco adapter picking it up and accessing the internet through it. Then a 2nd desktop with a LinkSys wireless card. Can the 2nd PC access the internet through the laptops connection? I know, why not just go from the 1st desktop? Let's say that I need to extend the wireless coverage. I'm in a straight line between all 3 machines and the 1st desktop's bubble isn't big enough to include the 2nd desktop. Can the laptop work to do that? How?